PgTI, the First Bioactive Protein Isolated from the Cactus Pilosocereus gounellei, is a Trypsin Inhibitor with Antimicrobial Activity

Abstract

Aims: This work aimed to isolate, characterize and evaluate the antimicrobial activity of a trypsin inhibitor (PgTI) from the stem of Pilosocereus gounellei. Place and Duration of Study: Methodology: PgTI was isolated from P. gounellei stem extract by gel filtration and ion exchange chromatographies. The inhibitor was characterized by isoelectric focusing, polyacrylamide gel electrophoresis, tryptic digestion followed by mass spectrometry analysis and for stability towards heating. Antibacterial and antifungal activities were investigated through broth microdilution assays. Viability of the microbial cells was also evaluated by flow cytometry analysis using thiazol orange and propidium iodide. Results: PgTI appeared as a single polypeptide band of 37.1 kDa and isoelectric point (pI) 5.88. The inhibition constant (K i ) for bovine trypsin was 14 nM and mass spectrometry analysis of PgTI did not reveal similarities with other plant proteins. Trypsin inhibitor activity was stable at temperatures up to 50ºC. PgTI inhibited growth of Gram-positive and Gram-negative bacteria (minimal inhibitory concentrations (MIC) from 7.5 to150 µg/mL) with bactericidal activity only against Escherichia coli (minimal bactericidal concentration: 75.0 µg/mL). PgTI also inhibited the growth of Candida krusei (MIC of 60 µg/mL). Flow cytometry confirmed that PgTI did not affect the viability of E. coli and C. krusei cells at the MIC. Conclusion: This is the first report on a bioactive protein purified from P. gounellei, which provides biotechnological value to this cactus.

Cryptococcus gattii Can Use the Cactus Pilosocereus spp. to Grow and Develop a Capsule and Produce Melanin In Vitro

“…Although it is unknown if Pilosocereus spp. contains any substances in the cortex that inhibit mitochondrial activity, other cacti species within this genus are known to have trypsin inhibitors, which could affect mitochondrial activity [35]. The presence of vesicles, such as deformations in the cells grown in all three cactus medias and PDB samples, were observed after performing India ink staining (Figure 2).…”

Food Plants in the Caatinga

“…The stem of P. gounellei contains an anionic trypsin inhibitor stable to 50 °C and active on medically important bacteria; the yeast, Candida krusei, may lessen the use of antibiotics and thus contribute to reduce the problem of antibiotic resistance. Outcomes reported have revealed new insights into the biochemistry of P. gounellei, increasing the biotechnological value of this plant (Rocha Filho et al 2019).…”